The sensations of hot and cold that humans experience are associated, on an atomic level, with “Brownian” molecular motion. Hotter temperatures are associated with more motion, while cooler temperatures are associated with less motion. “Absolute zero”, i.e., zero Kelvin (0 K), is associated with zero molecular motion.
With the development of laser cooling and other cold-atom technologies for controlling the motion of individual atoms, ultra-cold temperatures (below 1 K) have been achieved. Atoms in a vapor phase become ultra-cold as they are slowed, e.g., through the use of laser cooling. Among the practical applications is the development of more precise atomic clocks. Basic science has been advanced by the discovery of new techniques for manipulating atoms and discoveries of new states of matter, e.g., Bose-Einstein condensates.
To maintain an atom in an ultra-cold state, collisions with other atoms must be avoided. Collisions between atoms are most easily avoided when there are very few atoms to collide with each other. Therefore, cold-atom systems maintain their ultra-cold atoms in an ultra-high vacuum (UHV), i.e., at less than 10−9 torr.
In practice, a UHV requires a hermetically-sealed environment designed to prevent the entry and exit of atoms. Accordingly, it is preferable to generate the vapor-phase atoms within the vacuum environment rather than to introduce them from outside the vacuum environment. Vapor-phase atoms can be generated within a vacuum environment by heating a liquid or solid phase material including the atoms of interest. Heat required for the phase conversion can result from converting electrical energy introduced to the vacuum environment via feedthroughs, from converting optical energy introduced through transparent walls of the vacuum enclosure, or other means. However, while some species provide sufficient vapor pressure at room temperature for these applications, other species or atoms require temperatures in excess of several hundred degrees Celsius (° C.). To get a reservoir of atoms to this temperature requires increasing amounts of power to overcome cooling mechanisms such as convection over the cell body, or blackbody radiation. What is needed is an approach to dealing with problems associated with the generation of heat within a cold-atom system.